Decapsulation is a failure analysis step performed to open a plastic package to facilitate the  inspection, chemical analysis, or  electrical examination of the die and the internal features of the package.  If the package being opened is hermetic, then the process is referred to as 'delidding' or 'decapping.'  The techniques used for decapsulation are very different from those of delidding and decapping.


Delidding/decapping is a purely mechanical process. It may refer to the prying of the combo lid off a ceramic package, or the application of opposite torques to the top and bottom parts of the ceramic DIP to break the seal glass, or the cutting of the weld around a metal can.


On the other hand, the more widely used plastic decapsulation techniques are explained immediately below.


Manual Chemical Etching


Manual chemical etching consists of manually dispensing some acid on the surface of a package to remove the plastic material covering the die.   Red fuming nitric acid (HNO3) or sulfuric acid (H2SO4) is often used for this purpose.  A cavity is first milled on the top surface of the package.  Red fuming ntric acid heated to about 85-140 deg C or sulfuric acid heated to 140 deg C is then repeatedly dropped into the cavity to remove the plastic material covering the die.  When the die has been exposed adequately, the unit is rinsed with acetone then with D/I water, before being blow-dried carefully.


Manual etching may also refer to the process of soaking the package entirely in a beaker of sulfuric acid heated to about 140 deg C.  This process will totally destroy the unit, leaving behind the silicon die and bits and pieces of undissolved metal piece parts.  This is only used for die backside inspection for cracks.


Jet Etching


Jet etching is the automated version of chemical decapsulation, using a piece of equipment known as a jet etcher.  The jet etcher automatically squirts heated acid on the area of the package that needs to be removed.  During this process, the area to be etched is usually left exposed while the rest of the package topside is covered by a rubber mask.  Jet etchers usually use red fuming nitric acid heated to about 85 deg C.  Jet etching is superior to manual etching, being more controlled, efficient, and less messy.


Thermomechanical Decapsulation


There are instances wherein a plastic package has to be opened without using any acid, since acid is corrosive to the metallized areas on the die and can dissolve foreign materials on the die that may be of interest to the analyst.  A good alternative to chemical etching is thermomechanical decapsulation.  This technique involves heating the package followed by grinding, breaking, and cutting to separate the top part of the package from its bottom part.  This technique destroys the bond wires but preserves the die if used properly.


Plasma Etching


Plasma etching may also be used to expose the die of a plastic package.  Plasma etching removes plastic by making it react with a gas which can easily be vented out.  This requires expensive plasma etching machines but is very clean and selective.  It also takes longer compared to other techniques.


Fig. 1.  Photo of a Jet Etcher


See Also:  Failure AnalysisAll FA Techniques Optical Inspection;

Xray Radiography Sectioning SEM/TEM Acoustic MicroscopyWet Etching Recipes

FA Lab EquipmentBasic FA Flows Package FailuresDie Failures




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